GMAT Question of the Day - Daily to your Mailbox; hard ones only

 It is currently 15 Nov 2019, 08:34 ### GMAT Club Daily Prep

#### Thank you for using the timer - this advanced tool can estimate your performance and suggest more practice questions. We have subscribed you to Daily Prep Questions via email.

Customized
for You

we will pick new questions that match your level based on your Timer History

Track

every week, we’ll send you an estimated GMAT score based on your performance

Practice
Pays

we will pick new questions that match your level based on your Timer History

#### Not interested in getting valuable practice questions and articles delivered to your email? No problem, unsubscribe here.  # Math Revolution Approach (DS)

Author Message
Math Revolution GMAT Instructor V
Joined: 16 Aug 2015
Posts: 8141
GMAT 1: 760 Q51 V42 GPA: 3.82
Re: Math Revolution Approach (DS)  [#permalink]

### Show Tags

Is x^2>y^2?
1) x<y
2) -y>x

Ans: From the original condition, we can see that there are 2 variables. Hence, the correct answer is C.
_________________
Math Revolution GMAT Instructor V
Joined: 16 Aug 2015
Posts: 8141
GMAT 1: 760 Q51 V42 GPA: 3.82
Re: Math Revolution Approach (DS)  [#permalink]

### Show Tags

1
If a and b are non-negative integers, ab=?
1) 9^a=3^b
2) 5^a=2^b

ANS: From the original condition, there are 2 variables. Hence, there is a high chance that C is the correct answer. However, since this is an integer question, one of key questions, we should apply the common mistake type 4(A). From con 1), we get 2a=b. The answer is not unique and the condition is not sufficient. In case of con 2), we get a=b=0. The answer is unique and the condition is sufficient. Hence, the correct answer is B.
_________________
Math Revolution GMAT Instructor V
Joined: 16 Aug 2015
Posts: 8141
GMAT 1: 760 Q51 V42 GPA: 3.82
Re: Math Revolution Approach (DS)  [#permalink]

### Show Tags

1
If x, y are positive integers, what is the remainder when 2^(8x+y) is divided by 5?
1) x=1
2) y=2

ANS: From the original condition, there are 2 variables (x and y). In order to match the number of variables and the number of equations, we need 2 equations. Hence, there is a high chance that C is the correct answer. However, even though C is indeed the correct answer, since it is an integer question, one of the key questions, we have to apply the common mistake type 4(A). From the condition 2), the remainder of 2^(8x+y) is always 4. Hence, it is sufficient and the correct answer is B.
_________________
Math Revolution GMAT Instructor V
Joined: 16 Aug 2015
Posts: 8141
GMAT 1: 760 Q51 V42 GPA: 3.82
Re: Math Revolution Approach (DS)  [#permalink]

### Show Tags

Is x+y>0?
1) x>|y|
2) y<0
ANS: In case of con 1), from x>|y|≥-y, we get x>-y, x+y>0. The answer is yes and the condition is sufficient. Hence, the correct answer is A
_________________
Math Revolution GMAT Instructor V
Joined: 16 Aug 2015
Posts: 8141
GMAT 1: 760 Q51 V42 GPA: 3.82
Re: Math Revolution Approach (DS)  [#permalink]

### Show Tags

If x, y are positive integers, what is the unit digit of 2^(4x+2)+y?
1) x=1
2) y=2

ANS: In the original condition, there are 2 variables (x and y). Hence, there is a high chance that C is the correct answer. Using 1) & 2), C is the correct answer. However, since this is an integer question, we can apply the common mistake type 4(A). From con 2), the unit digit of 2^4x+2 is always 5. Hence, we only have to know y, and the condition is sufficient. The correct answer, thus, is B.
_________________
Math Revolution GMAT Instructor V
Joined: 16 Aug 2015
Posts: 8141
GMAT 1: 760 Q51 V42 GPA: 3.82
Re: Math Revolution Approach (DS)  [#permalink]

### Show Tags

If 0<x<y, is x<4?
1) (1/x)+(1/y)=1/2
2) 1/x>1/4

ANS: Since there are 2 variables in the original condition, there is a high chance that C is the correct answer. Condition 2) becomes the answer too easily because from 1/x>1/4, we get 0<x<4. The condition is sufficient. However, the condition is rather too hard. If we apply the common mistake type 4(B), the answer becomes D.
_________________
Math Revolution GMAT Instructor V
Joined: 16 Aug 2015
Posts: 8141
GMAT 1: 760 Q51 V42 GPA: 3.82
Re: Math Revolution Approach (DS)  [#permalink]

### Show Tags

Is a=b?
1) a^2=b^2
2) a=1

ANS: There are 2 variables in the original condition. In order to match the number of variables and the number of equations, we need 2 equations. There is a high chance that C is the correct answer. Using 1) & 2), from a=1 and b=-1, 1, the answer is both yes or no. Hence, the conditions are not sufficient and the correct answer is E.
_________________
Math Revolution GMAT Instructor V
Joined: 16 Aug 2015
Posts: 8141
GMAT 1: 760 Q51 V42 GPA: 3.82
Re: Math Revolution Approach (DS)  [#permalink]

### Show Tags

Is a=b?
1) a^2=b^2
2) a=1

ANS: There are 2 variables in the original condition. Hence, we need 2 equations, and there is a high chance that C is the correct answer. Using 1) & 2), from a=1 and b=-1, 1, the answer is both yes and no. The conditions are not sufficient and the correct answer is E.
_________________
Math Revolution GMAT Instructor V
Joined: 16 Aug 2015
Posts: 8141
GMAT 1: 760 Q51 V42 GPA: 3.82
Re: Math Revolution Approach (DS)  [#permalink]

### Show Tags

1
What is the perimeter of a certain right triangle?

1) The hypotenuse’s length is 5
2) The triangle’s area is 4.5

ANS: From the original condition, we can see that the number of variables is 2. Hence, the number of equations we need is 2 as well. The correct answer is C
_________________
Math Revolution GMAT Instructor V
Joined: 16 Aug 2015
Posts: 8141
GMAT 1: 760 Q51 V42 GPA: 3.82
Re: Math Revolution Approach (DS)  [#permalink]

### Show Tags

2^(x+y)/2^(x-y)=?
1) x=1
2) y=2

ANS: If we modify the original condition and the question, we get 2^(x+y)/2(x-y)=? --> 2^((x+y)-(x-y))=2^2y. We only have to know y and the correct answer is B.
_________________
Math Revolution GMAT Instructor V
Joined: 16 Aug 2015
Posts: 8141
GMAT 1: 760 Q51 V42 GPA: 3.82
Re: Math Revolution Approach (DS)  [#permalink]

### Show Tags

When a positive integer n is divided by 29, what is the remainder?
1) n-5 is divisible by 29
2) n-29 is divisible by 5

ANS: If we use direct substitution, in case of con 1), the remainder is always 5. The answer is unique and the condition is sufficient. Thus, the correct answer is A.
_________________
Math Revolution GMAT Instructor V
Joined: 16 Aug 2015
Posts: 8141
GMAT 1: 760 Q51 V42 GPA: 3.82
Re: Math Revolution Approach (DS)  [#permalink]

### Show Tags

Is |a^2-b^2|<10?
1) |a-b|<5
2) |a+b|<2

ANS: Since there are 2 variables in the original condition, the correct answer is C.
_________________
Math Revolution GMAT Instructor V
Joined: 16 Aug 2015
Posts: 8141
GMAT 1: 760 Q51 V42 GPA: 3.82
Re: Math Revolution Approach (DS)  [#permalink]

### Show Tags

Is a+b+c=even?
1) abc=even
2) ac=odd

ANS: Since there are 3 variables in the original condition, the correct answer is E.
_________________
Math Revolution GMAT Instructor V
Joined: 16 Aug 2015
Posts: 8141
GMAT 1: 760 Q51 V42 GPA: 3.82
Re: Math Revolution Approach (DS)  [#permalink]

### Show Tags

If b is an integer greater than 1, ab=?
1) b^a=1
2) b=2

ANS: Since there are 2 variables in the original condition, there is a high chance that C is the correct answer. However, we have to apply the common mistake type 4(A) since it is an integer question, one of key questions. In case of con 1), since we have a=0, we get ab=0. The answer is unique and the condition is sufficient. Hence, the correct answer is A.
_________________
Math Revolution GMAT Instructor V
Joined: 16 Aug 2015
Posts: 8141
GMAT 1: 760 Q51 V42 GPA: 3.82
Re: Math Revolution Approach (DS)  [#permalink]

### Show Tags

If a, b are positive integers (b≠1), is a/b<1/10 ?
1) a/(b-1)<1/15
2) (a-1)/b<1/15

ANS: Since there are 2 variables in the original condition, there is a high chance that C is the correct answer. Applying the common mistake type 4(A), the correct answer is A.
_________________
Math Revolution GMAT Instructor V
Joined: 16 Aug 2015
Posts: 8141
GMAT 1: 760 Q51 V42 GPA: 3.82
Re: Math Revolution Approach (DS)  [#permalink]

### Show Tags

(x-y)^2-(x+y)^2=?
1) xy=5
2) x+y=6

ANS: If we modify the original condition and the question, from (x-y)^2-(x+y)^2=? --> -4xy=? Hence, we only have to know the value of xy and the correct answer is A.
_________________
Math Revolution GMAT Instructor V
Joined: 16 Aug 2015
Posts: 8141
GMAT 1: 760 Q51 V42 GPA: 3.82
Re: Math Revolution Approach (DS)  [#permalink]

### Show Tags

If xy<0, is (x^2)y<0?
1) x>0
2) (x^3)y<0

_________________
Math Revolution GMAT Instructor V
Joined: 16 Aug 2015
Posts: 8141
GMAT 1: 760 Q51 V42 GPA: 3.82
Re: Math Revolution Approach (DS)  [#permalink]

### Show Tags

u=?
1) |u|+|v|=0
2) u^2+v^2=0

*ANS: There are 2 variables in the original condition and there is a high chance that C is the correct answer. Using con 1) and con 2), we get u=v=0. Hence the correct answer is D.
_________________
Math Revolution GMAT Instructor V
Joined: 16 Aug 2015
Posts: 8141
GMAT 1: 760 Q51 V42 GPA: 3.82
Re: Math Revolution Approach (DS)  [#permalink]

### Show Tags

How many 5 existed in the 11 numbers?
1) The average (arithmetic mean) of the 11 numbers is 5
2) The median of the 11 numbers is 5

*ANS: If we modify the original condition and the question, since we have 11 numbers, the median exists in these numbers. Hence, if we look at the condition 2), since the median is 5, 5 is always a part of 11 numbers. The answer is yes and the answer is B.
_________________
Math Revolution GMAT Instructor V
Joined: 16 Aug 2015
Posts: 8141
GMAT 1: 760 Q51 V42 GPA: 3.82
Re: Math Revolution Approach (DS)  [#permalink]

### Show Tags

Is xy<10?
1) x<5
2) y<2

ANS: There are 2 variables (x and y) and there is a high chance that C is the correct answer. Using con 1) and 2), the answer is yes when xy=1 and the answer is no when x=y=-5. Hence, the condition is not sufficient. So, the correct answer is E.
_________________ Re: Math Revolution Approach (DS)   [#permalink] 04 Aug 2016, 19:21

Go to page   Previous    1   2   3   4   5   6   7   8   9   10   11  ...  29    Next  [ 573 posts ]

Display posts from previous: Sort by

# Math Revolution Approach (DS)

Moderator: souvonik2k  